Nothing lasts forever!
14mnth olds are demanding and have temper tantrums regardless of how they are fed - she seems like she is shaping up nicely to be a typical 2 year old. It can be frustrating though. There are times as a mother that you just feel "mauled" all day long - what you wouldn't do for 5 minutes peace and quiet.
Can you see it from her point of view? A breastfeed has got everything a cuddle has got - but more. It's a supersized cuddle! It fixes scraped knees, puts you to sleep and stops that tantrum mid scream. And no-one told her the rules had changed - that for 14mnth olds feeding according to need isn't cool any more.
Try to separate (in your mind) the feeding from normal baby behaviour. It's fine to teach some manners around breastfeeding at this age. Above all - all of this is normal and will pass